Pre heat the oven to 150ºC (fan assisted)
Halve the plum tomatoes and place them on a roasting tray along with the unpeeled garlic. Drizzle a little olive oil on top of the tomatoes and roast in the oven for an hour.
Wash the rose petals to insure there are no bugs, leaves or stems and pat dry. Set aside.
In a pan over a medium heat, roast the cumin and coriander seeds for a few minutes. You will know when they are done when you smell the fragrance of the spices. Once done, immediately transfer to a plate to cool.
In the same pan over a medium heat, roast the red chillies for a few minutes. You will know when they are done when the colour changes to a deeper red and a bit brownish (see the how-to video) Once ready, transfer immediately into a bowl. Pour boiling water over the chillies and cover to hydrate. Set aside for 10 minutes.
Grind the cumin and coriander.
Once the chillies are soft, put on some gloves and remove stems and cut into half or into three. Remove some or all of the seeds if you dont want the harissa to be too hot.
Wash the jam jars with hot soapy water and leave to drain.
Once the tomatoes are ready, turn the oven down to 100ºC. Sterlise the jam jars and lids for a minimum of half an hour.
In a blender or food processor add the chillies, tomatoes, peeled garlic, salt and sugar and blend to a rough paste.
Add the rose petals, 40 gms olive oil, lemon juice, rose water and apple cider vinegar and blend to a rough paste.
Spoon into sterilised bottles, cover with a layer of olive oil and seal with the lid.